The matrix metalloproteinases (MMP's) are a family of zinc containing endopeptidases which are capable of cleaving large biomolecules such as the collagens, proteoglycans and gelatins. Expression is upregulated by pro-inflammatory cytokines and/or growth factors. The MMP's are secreted as inactive zymogens which, upon activation, are subject to control by endogenous inhibitors, for example, tissue inhibitor of metalloproteinases (TIMP) and α2-macroglobulin. Chapman, K. T. et al., J. Med. Chem. 36, 4293–4301 (1993); Beckett, R. P. et al., DDT 1, 16–26 (1996). The characterizing feature of diseases involving the enzymes appears to be a stoichiometric imbalance between active enzymes and endogenous inhibitors, leading to excessive tissue disruption, and often degradation. McCachren, S. S., Arthritis Rheum. 34, 1085–1093 (1991).
The discovery of different families of matrix metalloproteinase, their relationships, and their individual characteristics have been categorized in several reports. Emonard, H. et al., Cell Molec. Biol. 36, 131–153 (1990); Birkedal-Hansen, H., J. Oral Pathol. 17, 445–451 (1988); Matrisian, L. M., Trends Genet. 6, 121–125 (1990); Murphy, G. J. P. et al., FEBS Lett. 289, 4–7 (1991); Matrisian, L. M., Bioessays 14, 455–463 (1992). Three groups of MMPs have been delineated: the collagenases which have triple helical interstitial collagen as a substrate, the gelatinases which are proteinases of denatured collagen and Type IV collagen, and the stromelysins which were originally characterized as proteoglycanases but have now been identified to have a broader proteolytic spectrum. Examples of specific collagenases include fibroblast collagenase characterized as proteoglycanases but have now been identified to have a broader proteolytic spectrum. Examples of specific collagenases include fibroblast collagenase (MMP-1), neutrophil collagenase (MMP-8), and collagenase 3 (MMP-13). Examples of gelatinases include 72 kDa gelatinase (gelatinase A; MMP-2) and 92 kDa gelatinase (gelatinase B; MMP-9). Examples of stromelysins include stromelysin 1 (MMP-3), stromelysin 2 (MMP-10) and matrilysin (MMP-7). Other MMPs which do not fit neatly into the above groups include metalloelastase (MMP-12), membrane-type MMP (MT-MMP or MMP-14) and stromelysin 3 (MMP-11). Beckett, R. P. et al., supra.
Over-expression and activation of MMPs have been linked with a wide range of diseases such as cancer; rheumatoid arthritis; osteoarthritis; chronic inflammatory disorders, such as, for example, emphysema; cardiovascular disorders, such as, for example, atherosclerosis; corneal ulceration; dental diseases such as, for example, gingivitis; periodontal disease; neurological disorders, such as, for example, multiple sclerosis; and smoking-induced emphysema.
For example, in adenocarcinoma, invasive proximal gastric cells express the 72 kDa form of collagenase Type IV, whereas the noninvasive cells do not. Schwartz, G. K. et al., Cancer 73, 22–27 (1994). Rat embryo cells transformed by the Ha-ras and v-myc oncogenes or by Ha-ras alone are metastatic in nude mice and release the 92 kDa gelatinase/collagenase (MMP-9). Bernhard, E. J. et al., Proc. Natl. Acad. Sci. 91, 4293–4597 (1994). The plasma concentration of MMP-9 was significantly increased (P<0.01) in 122 patients with gastrointestinal tract cancer and breast cancer. Zucker, S. et al., Cancer Res. 53, 140–146 (1993). Moreover, intraperitoneal administration of batimastat, a synthetic MMP inhibitor, gave significant inhibition in the growth and metastatic spread and number of lung colonies that were produced by intravenous injection of the B16-BL6 murine melanoma in C57BL/6N mice. Chirivi, R. G. S. et al., Int. J. Cancer 58, 460–464 (1994). Over-expression of TIMP-2, the endogenous tissue inhibitor of MMP-2, markedly reduced melanoma growth in the skin of immunodeficient mice. Montgomery, A. M. P. et al., Cancer Res. 54, 5467–5473 (1994).
Accelerated breakdown of the extracellular matrix of articular cartilage is a key feature in the pathology of both rheumatoid arthritis and osteoarthritis. Current evidence suggests that the inappropriate synthesis of MMPs is the key event. Beeley, N. R. A. et al., Curr. Opin. Ther. Patents, 4(1), 7–16 (1994). The advent of reliable diagnostic tools have allowed a number of research groups to recognize that stromelysin is a key enzyme in both arthritis and joint trauma. Beeley, N. R. A. et al., Id.; Hasty, K. A. et al., Arthr. Rheum. 33, 388–397 (1990). It has also been shown that stromelysin is important for the conversion of procollagenase to active collagenase. Murphy, G. et al., Biochem. J. 248, 265–268 (1987).
Furthermore, a range of MMPs can hydrolyse the membrane-bound precursor of the pro-inflammatory cytokine tumor necrosis factor .alpha. (TNF-α). Gearing, A. J. H. et al., Nature 370, 555–557 (1994). This cleavage yields mature soluble TNF-α and the inhibitors of MMPs can block production of TNF-α both in vitro and in vivo. Gearing, A. J. H. et al., Id.; Mohler, K. M. et al., Nature 370, 218–220 (1994); McGeehan, G. M. et al., Nature 370, 558–561 (1994). This pharmacological action is a probable contributor to the antiarthritic action of this class of compounds seen in animal models. Beckett, R. P. et al., supra.
Stromelysin has been observed to degrade the α1-proteinase inhibitor that regulates the activity of enzymes such as elastase, excesses of which have been linked to chronic inflammatory disorders such as emphysema and chronic bronchitis. Inhibition of the appropriate MMP may thus potentiate the inhibitory activity of endogenous inhibitors of this type. Beeley, N. R. A. et al., supra.; Wahl, R. C. et al., Annual Reports in Medicinal Chemistry 25, 177–184 (1990).
High levels of mRNA corresponding to stromelysin have been observed in atherosclerotic plaques removed from heart transplant patients. Henney, A. M., et al., Proc. Natl. Acad. Sci. 88, 8154–8158 (1991). It is submitted that the role of stromelysin in such plaques is to encourage rupture of the connective tissue matrix that encloses the plaque. This rupture is in turn thought to be a key event in the cascade that leads to clot formation of the type seen in coronary thrombosis. MMP inhibition is thus a preventive measure for such thromboses.
Collagenase, stromelysin and gelatinase have been implicated in the destruction of the extracellular matrix of the cornea. This is thought to be an important mechanism of morbidity and visual loss in a number of ulcerative ocular diseases, particularly those following infection or chemical damage. Burns, F. R. et al., Invest. Opthalmol. and Visual Sci. 32, 1569–1575 (1989). The MMPs present in the eye during ulceration are derived either endogenously from infiltrating leucocytes or fibroblasts, or exogenously from microbes.
Collagenase and stromelysin activities have been identified in fibroblasts isolated from inflamed gingiva and the levels of enzyme have been correlated with the severity of the gingivitis observed. Beeley, N. R. A. et al., supra.; Overall, C. M. et al., J. Periodontal Res. 22, 81–88 (1987).
Excessive levels of gelatinase-B in cerebrospinal fluid has been linked with incidence of multiple sclerosis and other neurological disorders. Beeley, N. R. A. et al., supra.; Miyazaki, K. et al., Nature 362, 839–841 (1993). The enzyme may play a key role in the demyelination of neurons and the breakdown of the blood brain barrier that occurs in such disorders.
In addition, a recent study indicates that MMP-12 is required for the development of cigarette smoke-induced emphysema in mice. Science, 277, 2002 (1997).
Apart from the role of these potentially very destructive enzymes in pathology, the MMPs play an essential role in cell regrowth and turnover in healthy tissue. Broad-spectrum inhibition of the MMPs in the clinical setting results in musculoskeletal stiffness and pain. H. S. Rasmussen and P. P. McCann, Pharmacol. Ther., 75, 69–75 (1997). This side effect and others associated with broad-spectrum inhibition may be enhanced in chronic administration. Thus, it would be advantageous to provide selective MMP inhibitors.
Molecules that have been identified as inhibiting the activity of matrix metalloproteinases include cyclic and heterocyclic N-substituted alpha-imino hydroxamic and carboxylic acids, such as those described in EP 0861236, incorporated herein by reference. Current processes for preparing these types of molecules, however, suffer from a number of drawbacks in that, for example, they have a high number of steps and produce a relatively low yield of product. In addition, the prior art processes typically use carcinogenic intermediates such as nitrobiphenyls, which lead to racemates or partly racemized compounds that require subsequent separation of the enantiomers. Further, the intermediates used often have to be purified by column chromatography, which is not amenable to the mass production levels required by pilot plant or production operations. Accordingly, there is a need in the art for a process for preparing cyclic and heterocyclic N-substituted alpha-imino hydroxamic and carboxylic acids that does not suffer from such drawbacks.